Interface formation and strengthening mechanisms of Al/Mg bimetallic composite via compound casting with rare earth Ce introduction

Abstract

The microstructures and mechanical properties of the existing Al/Mg bimetallic composite interface prepared by compound casting process were expected to be improved. Through a process of adding the Mg–Ce master alloy during the Mg alloy smelting, the purpose of introducing rare earth element, Ce, into the Al/Mg bimetallic composite interface was realized. With the introduction of the Ce, the microstructure evolution mechanism and mechanical properties strengthening mechanism of the Al/Mg bimetallic interface were studied in detail. Two typical rare earth phases containing Ce, needle-like and rod-shaped Al11Ce3 and block-like Al8Mn4Ce, precipitated in the eutectic area (E area) at the Al/Mg interface, and became more with the increase of the Ce addition. The precipitation of the rare earth phases made the original eutectic cluster structures and primary γ (Mg17Al12) dendrites refine, and the secondary γ phase precipitate more. However, there were no obvious changes in the intermetallic compounds area (IMC area) of the Al/Mg bimetallic interface. The grain refinement strengthening and precipitation strengthening, mainly brought from the E area, improved the bonding strength of the Al/Mg interface. When the content of the Ce was 1.0%, the average bonding strength of the Al/Mg bimetallic interface increased from 37.22 MPa when it was not added Ce to 53.29 MPa, reaching the maximum increase of 43.18% in the studied contents. However, when the addition of the Ce continued to increase, a large number of the rare earth phases precipitated, causing stress concentrations, intensifying the separation of the interface matrix structures and reducing the bonding strength of the Al/Mg interface.